There's a huge difference in performance. There's also a huge difference in price. If you can afford it, go for an SSD.

A relatively cost effective solution is to get a smallish SSD (say 128 GB), install the system to it, plus install the applications you want to be the speediest, and keep all your files and other apps on a HDD.

This wouldn't be practical on a laptop, but for a desktop is a very good option.

They're getting better, from what I've read, and most disks spend relatively little time writing anyway. It's not just boot times of course - apps starting more or less instantly is great too. Those times when your machine seems to crawl while multiple apps request stuff off the disk are gone too, e.g. if you start a load of stuff at boot. I'd love one for my fossil work laptop.

It's also worth having a Google around for the many speed test benchmarks, and choosing the fasted you can afford, once you've picked your size between 128 and a costly (in 2011) 256GB.

In a laptop, the performance difference in addition to the battery life benefits mean that I'd wholeheartedly recommend one in the current HDD pricing climate.

GO FOR IT, and you wont be disappointed. Just keep system backups on an HDD once you've set everything up, in case anything goes wrong. The drive will probably have a multi-year manufacturer's warranty, but that wont help you to restore your system in case it fails.

Saying that, the OP should also check the manufacturer's website with the HDD serial number handy, in case they'll swap it for a new one for free.

I believe that WD have a 3 year warranty as standard. Not sure about the others.

Had an intel SSD in my normal PC which was fookin great. Just bought a new laptop with a 1.5 tb raid 0 array across two disks, so If I had bigger balls I'd void the warranty and switch out one of the disks for the intel.

SSD's are for things that need fast seek times on random bits within a data series so they are greatly beneficial to running programs with and it's the area they are best suited to. So you place your OS and games on that drive you use the most.

If your just loading up a film to watch for example then you won't see much of an improvement in load times over a traditional hard drive as it's seeking a continuous steam of data rather than searching for bits scattered over the drive and in that situation your better off with the traditional platter based hard drive.